Linking Space Station & Mars: the IMUSE Strategy (1985)

John Niehoff was manager of the Space Sciences Department at Science Applications International Corporation (SAIC) in Schaumburg, Illinois, when he presented his Integrated Mars Unmanned Surface Exploration (IMUSE) strategy to the National Academy of Science Space Science Board Major Directions Summer Study on 30 July 1985. He proposed employing reusable automated spacecraft with designs “deeply rooted” in planned U.S. space station technology to carry out a complex, evolving series of automated Mars Sample Return (MSR) missions between 1996 and 2016.

His work had its origins in the 1984 joint Jet Propulsion Laboratory/NASA Johnson Space Center MSR study and the work of the National Commission on Space (NCOS), a blue ribbon panel appointed by President Ronald Reagan to chart a future for the U.S. in space. Niehoff and SAIC provided both the JPL/JSC MSR study and NCOS with planning and engineering support.

Niehoff explained that linking MSR with the Space Station Program would integrate it with “other capabilities and objectives of the larger space program.” It would also create a bridge between early 1990s Earth-orbital station operations and a piloted Mars landing by the early 2020s.

At the time Niehoff made his presentation, the Space Station Program was just 18 months old. Reagan had used his January 1984 State of the Union Address to launch (in a bureaucratic sense, at least) the manned space laboratory. He gave the space agency until 1994 to complete the Space Station. NASA and its contractors studied a range of possible station configurations in 1984-1985. Six months after Niehoff’s presentation, in early 1986, NASA settled on the ambitious Dual Keel station design (in spite of the 28 January 1986 Challenger accident). The Dual Keel would provide ample facilities for space construction and satellite servicing and a home base for space tugs that could launch or retrieve spacecraft and satellites.

Niehoff’s IMUSE spacecraft – which he dubbed an Interplanetary Platform (IP) – would transport smaller vehicles between Earth and Mars. It would provide them with “keep-alive” solar cell-generated electrical power, thermal control, course-correction propulsion, and other requirements typically provided by a throwaway spacecraft bus. The IP would cut costs over the course of the IMUSE program because it would need to be launched onto its interplanetary path only once. As the IP flew without stopping past Mars or Earth, the smaller vehicles would separate to land on or go into orbit around the planet or would leave the planet to rendezvous and dock with the IP.

He described a pair of IMUSE scenarios. In both, the IP would follow Versatile International Station for Interplanetary Transport (VISIT) cycler orbits, which would, Niehoff explained, be “simultaneously resonant with both Earth and Mars.” A spacecraft in a VISIT-1-type orbit would circle the Sun in 1.25 Earth years, which meant that it would encounter Earth four times in five Earth years and Mars three times in two Mars years. A VISIT-2-type orbit, on the other hand, would need 1.5 Earth years to complete. A spacecraft on a VISIT-2 path would encounter Earth twice in three Earth years and Mars five times in four Mars years.

Niehoff’s first IMUSE scenario would begin with Earth-orbit departure of one 6340-kilogram IP – possibly pushed by a Space Station-based space tug – in May 1996. During its first Mars encounter (December 1997), the IP would drop off a 400-kilogram “smart rover” capable of complex autonomous operations and a 1110-kilogram communications orbiter for relaying radio signals between Mars and Earth. The rover and orbiter, packed separately in identical 2570-kilogram streamlined aerocapture vehicles, would skim the martian atmosphere to slow down so that Mars’s gravity could capture them into orbit.

The rover would then descend to Mars’s surface atop a 1170-kilogram “generic lander” capable of precision landing. After rolling off the lander onto the surface, it would employ a variety of scoops, picks, and drills to gather rock, sand, and dust samples.

In April 2001, a second rover and two 4300-kilogram Mars ascent vehicles would rendezvous and dock with the IP as its Sun-centered orbit carried it past Earth for the first time. This would demonstrate “hyperbolic rendezvous” ahead of its use in the piloted Mars program. Hyperbolic rendezvous would occur not in Mars or Earth orbit, but rather in the IP’s orbit around the Sun. The technique would save propellants because the IP would not fire rocket motors to capture into and escape from Earth or Mars orbit.

Seven months later (November 2001), the IP would swing by Mars for the second time and drop off the 2001 rover, which would land at a new site on Mars. Ascent vehicle #1, meanwhile, would land near the 1996 rover and ascent vehicle #2 would set down near the 2001 rover.

Earth would not be positioned properly for the IP to make a direct return after the November 2001 Mars encounter, so the IP would orbit the Sun twice and return to Mars for the third time in July 2005. Ascent vehicle #1 would lift off from Mars bearing the 10 kilograms of samples the 1996 rover collected and ascent vehicle #2 would lift off bearing 2001 rover samples. The ascent vehicles would perform hyperbolic rendezvous and dock with the IP as Mars slowly shrank behind the three spacecraft.

In April 2006, the IP would swing by Earth for the second time to drop off the Mars samples it had collected 10 months earlier. A Space Station-based tug would rendezvous and retrieve the samples after they aerocaptured into Earth orbit. The IP would also pick up ascent vehicle #3 and two 2000-kilogram automated Mars surface stations. It would release these during its fourth Mars encounter in April 2009. Ascent vehicle #3 would land close to the still-operational 1996 rover. The surface stations would land at separate sites, bringing to four the number of Mars landing sites explored in the IMUSE program. The stations would conduct life science experiments, test manufacture of propellants from martian resources, and study the effects on spacecraft materials of long exposure to martian surface conditions.

During its third Earth encounter (April 2011), the IP would pick up a “manned precursor payload” consisting of equipment and supplies for the first piloted Mars landing expedition. It would drop off the manned precursor payload in December 2013, during its fifth Mars encounter, and pick up samples from the 1996 rover launched from Mars by ascent vehicle #3. In April 2016, the IP would encounter Earth for the fourth time and drop off the samples.

Niehoff’s second IMUSE scenario would include two IPs. These would deliver the same payloads to Mars in the same manner as his first scenario, but at an accelerated rate. The first IP would leave Earth in July 1998 and fly past Mars in February 2000, November 2003, August 2007, and May 2011. It would encounter Earth in July 2003, July 2008, and July 2013. IP #2 would leave Earth in April 2001, fly past Mars in November 2001, July 2005, and April 2009, and encounter Earth in April 2006 and April 2011.

IMUSE scenario #2 would return the first Mars samples to Earth in April 2006 and drop off the first manned precursor payload at Mars in May 2011. The piloted program, which would employ large cycling spacecraft based on Space Station modules to rotate crews to and from a long-term Mars surface outpost, would commence shortly thereafter.

Candidate exploration site: topographic image of Hadley Crater, Mars, from the European Space Agency’s Mars Express orbiter. The main crater (red floor) is about 120 kilometers across. The deepest part of the crater complex (shown in purple) is a likely window into Mars’s distant past. Image: ESA/DLR/FU Berlin (G. Neukum)

Beyond Apollo chronicles space history through missions and programs that didn’t happen. It is not meant to be in any way discouraging; rather, it is intended to inform and inspire. Comments are encouraged. Off-topic comments might be deleted.

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